Question

How can I convert short int[] to char*?

short int test[4000];
char* test2;

I tried this:

test2 = (char*)test[4000]

Error–> PTR is not valid

Answer 1

So you have a buffer in form of an array, and you want to write the binary contents of it into a file. You do it like this:

if (fwrite(test, sizeof(test), 1, f) < 1)
{
    // handle error here (write failed)
}

fwrite() function is used to write binary data to files (and fread() to read). It takes a void* pointer, so it can work with any type (and C++ implicitly converts any other pointer/array to it).

The sizeof(test) determines the exact size of the array. If you don’t want to write the whole of it (i.e. just filled part of it), you want to use sizeof(short) * N, where N is the number of filled elements.

1 here means that there is one block of data to write; so fwrite() will write the whole data at once. f is the file you’re writing to. And it returns the number of blocks written (so 1 on success and 0 on failure).

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For completeness, I should note that’s only one of the approaches to use of fwrite(). It may be a bit more semantic to use something like:

fwrite(test, sizeof(short), N, f)

but then the fwrite() may actually write only part of the data, and you will need to care about that. In other words, if it returned less than N, you’d have to retry writing the remaining part.